The Editors of Encyclopaedia Britannica. Sergius II. „A story that Pope Sergius IV (1009–12) sent Sergius II the Synodicon, a letter insisting on the Latin Trinitarian teaching that the Holy Spirit relates to both Father and Son (Filioque), thus initiating the Eastern schism when Patriarch Sergius reacted by erasing the pope’s name from the Byzantine prayer intercessions, is the invention of 12th-century controversialists.”
